1. Field of the Invention
The present invention relates to field emission technology and, more particularly, to a field emission cathode and a field emission device employing the same.
2. Discussion of the Related Art
Field emission devices operate based on emission of electrons in a vacuum and the subsequent impingement of those electrons on a fluorescent layer, thereby producing illumination. Electrons are emitted from micron-sized tips (i.e. field emitters) in a strong electric field. The electrons are accelerated and then collide with the fluorescent material, thereby producing the light. Field emission devices are thin and light and capable of providing high brightness.
As shown in FIG. 5, a conventional field emission diode 6 generally includes a flat panel cathode 60 and an anode 64 opposite from the cathode 60. Isolating spacers 63 are interposed between the cathode 60 and the anode 64. The cathode 60 includes an electrically conductive flat panel base 61 and a plurality of field emitters 62 formed thereon.
A triode field emission device is another common type of the field emission device. Compared to the diode field emission device, the triode field emission device further includes a grid electrode located between the cathode 60 and the anode 64.
FIG. 6 shows a typical triode field emission device 7. The triode field emission device 7 employs carbon nanotubes 75 as emitters. A first metal film 71 is formed on a back substrate 70 and serves as a cathode. An isolating layer 72 and a second metal film 73 are formed on the first metal film 71. The isolating layer 72 and the second metal film 73 each include a plurality of tiny through holes, such through holes being configured for exposing portions of the first metal film 71. Electrically conductive polymer films 74 are formed on the exposed portions of the first metal film 71 in the through holes. A plurality of carbon nanotubes 75 is formed on the films 74. Spacers 76 are disposed on the second metal film 73. A front substrate including a transparent anode 78 and a fluorescent layer 77 are correspondingly formed on the spacers 76.
However, the above-described field emission devices 6 and 7 both employ flat panel bases for carrying the field emitters. The field emitters are generally densely arranged. Most of the neighboring emitters can become tangled with each other. Therefore, a shielding effect between the adjacent emitters is undesirably enhanced. The performance of the field emission device is impaired, accordingly.